Earlier quoted context omitted.
Because it's deterministic, accurate, and correct. All of which the LLM would be unable to do.
Does deterministic matter if its accurate or correct?
Does it matter if I answer every question with either 1 or 2 and flip a coin each time to decide which?
Deterministic means that if it is accurate/correct once, it will continue to be in future runs (unless the correct answer changes; a stopped clock is deterministic).